Under existing standards, one can store whole blood for processing (to produce platelets and other blood products) for up to 24 hours at room temperature, provided the blood is rapidly cooled to 22±2° C. After collecting blood in blood bags, this rapid cooling is conventionally performed using cooling plates filled with butane-1,4-diol—a gel that melts at a temperature of 20° C. In gel phase, butane-1,4-diol absorbs heat from freshly collected blood. When the gel temperature reaches its phase change (melting) temperature, butane-1,4-diol can then absorb a lot of heat while maintaining a constant temperature of 18° C. This phase change material accumulates heat until it turns into a liquid. Afterwards, when brought back to a cooler ambient temperature, butane-1,4-diol returns to a solid gel state and releases stored heat.
By absorbing heat from blood, butane-1,4-diol allows rapid cooling (within 2 hours) of blood bags from 37° C. to 22±2° C. and maintenance of a constant temperature afterwards. Rapid cooling of blood bags ensures adequate blood product quality before component preparation. Butane-1,4-diol cooling plates were commercially introduced by NPBI in the early 1990's, following the work of Pietersz et al., “Storage of whole blood for up to 24 hours at ambient temperature prior to component preparation,” Vox Sang 1989; 56(3): 145-50. Currently, Fresenius HemoCare (Redmond, Wash., USA) offers two cooling and transport systems for blood bags: Compocool, and a more recent version, Compocool II™/Compocool WB™, in which the butane-1,4-diol cooling unit is placed in an insulated crate. Additionally, Sebra/Haemonetics (Tucson, Ariz., USA) offers butane-1,4-diol-filled transparent pouches (ThermaSure), developed for the transport of platelet concentrates and blood units at 22±2° C.
The use of cooling plates containing butane-1,4-diol presents logistics issues for blood collection at remote sites. These cooling plates must be conditioned for at least 9 hours at a temperature of 4±2° C. before transport to the collection site. After conditioning, plates must be brought to 14-11.6° C. to prevent deleterious effects on the blood; this pre-warming step can take up to 60 minutes. Furthermore, since the heat-absorbing capacity of butane-1,4 diol declines in ambient temperatures that exceed 18° C., the performance of the plates gradually decreases in parallel with time of storage at ambient temperature. Additionally, ambient temperatures for the plates (i.e., during transport to the blood processing site) should ideally be in the 10-30° C. range. At an ambient temperature of −35° C., it has been shown that the Compocool II system is unable to maintain the desired temperature of blood bags for more than 2 hours. Thus, at such temperature extremes, blood bags must be transported in temperature-controlled units, as temperatures less than 20° C. are deleterious to platelet yield and quality—where platelets are produced from the blood.
Finally, butane-1,4-diol has to be periodically replaced, because it absorbs humidity over time, which alters its melting temperature and heat-absorbing characteristics.
Thus, a new system for rapid cooling and maintenance of freshly donated blood which avoids the disadvantages of butane-1,4-diol systems, and which can be readily fabricated, is needed.